The present invention, which has a multi-application usage, generally pertains to a method for non-invasively and remotely sensing of visible and invisible moving bodies or objects, even those hidden in immune barriers and concealed locations.
Detection of movement occurs by tracking any variation in the Radio Frequency (RF) impedance match of a scrutinized media in which the targeted object is located, with a power RF transmitter. (xe2x80x9cMedia,xe2x80x9d in the context of these documents, will mean the environment close to the moving body or object under inspection. xe2x80x9cTargeted objectxe2x80x9d will mean the moving body or object under inspection.)
A stable power Electro-Magnetic (EM) field, at a fixed frequency (High range), is created around the targeted object. By extracting the slight power changes from the resultant forward and reflected powers generated within the transmitting line (coaxial cable, dual parallel wires, or strip lines) that transfers and carries the transmitted EM-energy, any movement of the targeted object within the media can be detected.
By way of example and not of limitation, the method of the present invention comprises usage in the following applications:
1. In the agricultural field by a device for detection of early infestation by red palm weevil and tunnel borers in tree trunks and upper roots. This application is particularly important where the insect larvae secretly and silently consume the tree""s core, producing tunnels and hollows that lead to the death of the tree.
Detection of early infestation is vital but extremely difficult, and by the time the evidence of presence of the pest becomes apparent, it is too late to save the tree. Unless the infestation is detected and treated at early stage, the life of the tree is limited to a few months.
Present research indicates that this pest seriously threatens untold millions of palm and fruit trees all over the world and unless this problem is effectively resolved very soon, the likelihood is that all trees in afflicted areas will die within a few years.
2. In the medical field, this method can be implemented in various applications, such as a device for real-time monitoring of the heart""s motion (kinetocardiograph). There is no direct contact of device circuits to the human body. Data drawn from this method will add new parameters in the field of medicine for more versatile and comprehensive diagnosis of heart problems.
The principal present-day methods for heart monitoring are:
Electrocardiograph (ECG), which monitors the heart activity by tracking the electrical signals generated by the chemical reaction of the heart muscles. This method employs the use of electrodes directly attached to the patient.
Phonocardiogragh (PCG), which audibly indicates the heart motion. This method involves the use of a microphone placed directly on the patient.
Doppler Cardiograph (DCG) monitors the heart activity using the ultrasound Doppler effect. This method employs the use of an ultrasound probe in contact with the patient""s body under specific conditions.
All of the foregoing methods are measuring reactions to the heart""s motion, and all require direct contact with the patient by electrodes, etc.
The present invention has the following advantages by monitoring the heart:
In real time.
Directly, without dependence on reaction.
Does not require any direct contact with the patient.
Monitors the motion activity of xe2x80x9callxe2x80x9d of the components of the heart.
Additionally, the method can also be used as a device for continuous monitoring of newborn, premature babies, and patients under intensive care. All the present-day methods require direct contact with the patient/baby, either in the form of contact electrodes or pressure sensor mattresses, but they are impractical in the case of premature babies, due to the frequent requirement to move the baby for feeding, cleaning, etc.
The device can also be utilized to give an early alarm, whenever a life-threatening situation arises, such as: Sudden Infant Death Syndrome (SIDS), by continuous and precise remote monitoring of the movement of vital organs, such as lungs in the breathing process. This will accelerate emergency intensive care.
Since the device is monitoring the organ activity remotely, it does not require attachment of electrodes etc to the body. The data drawn from this device can also be collated for analytical evaluation for diagnostic purposes.
Non-invasively and remotely monitoring of the human vital signs or body movements are necessary in the following additional circumstances:
Where burn patients cannot tolerate the attachment of electrodes directly to the skin surface.
Where disaster victims are trapped and concealed in building debris following building collapse.
Where it is essential to know and react to the condition of aircraft pilots and astronauts when there is a possibility of temporary xe2x80x9cblack outxe2x80x9d due to extreme maneuvers in flight.
3. This method also will be used to detect sudden instability in flow of liquids, for example, blood through tubes in open-heart surgery and dialysis treatment, by non-invasively sensing the flow intensity of the liquid.
This new method will provide a mechanism to monitor and sense the slightest unexpected change in flow process. This will guarantee, for example, not to have any air bubble leakage into blood path, and at the same time protecting it from thrombosis and contamination, since this is done by non-invasive sensing without any direct contact.
4. Another application will be in concealed security systems for protection against thieves and intruders, through sensing body movements in corridors or regions that need protection. The sensors can be hidden underground or inside or in back of the walls, even cement ones, so that they can not be located and disabled by intruders.
5. Automatic access control is also an area where the method will be effectively used, since most existing automatic outdoor control systems are affected by light/darkness, dust, heat, etc.
Another example is monitoring and controlling traffic and traffic signals by sensing vehicle movements in road traffic activity.
From the necessarily limited examples given above, it will be seen that the method has a very wide spectrum of applications.
It is an established fact that the optimum transfer of EM-energy from an RF transmitter to the load occurs when the output impedance of the transmitter matches the load impedance.
The popular method used to predict the level of match is achieved by sampling the actual values of the forward and the reflected powers generated within the transmission-line that transfers and carries the transmitted EM-energy, these values can be easily picked up by passing the transmitted RF power through a bidirectional coupler. The picked-up power values are represented by the bidirectional coupler in voltage form, so the presented values will be the forward VF and reflected VR voltages.
The measured VF and VR voltages are then combined together by special equations (mathematical formulas) to produce a nominal calculated value. This value will reflect in one way or another the real match level.
Voltage Standing Wave Ratio (VSWR) is the most common expression to indicate the degree of match:
VSWR=(VF+VR)/(VFxe2x88x92VR)xe2x80x83xe2x80x83(1)
Also there are other widely used expressions, which demonstrate the actual match level. These expressions are the reflection coefficient (xcfx81) and the return loss coefficient, and many more.
When a stable power RF generator is used to transmit EM-energy at a stable load (media), and where the RF generator output impedance and the load impedance have almost identical values, then the resulting level of match will also be stable. When the load (media) or a part of it moves within the transmitted EM-field, then the total resultant characteristic impedance of the load will vary positively or negatively, this move will also vary the match level, according to how the match or mismatch occurs.
The method of the present invention can be precisely described as follows:
Stable EM-energy is applied to a scrutinized media containing the inspected target by a balanced type antenna. The EM-current flow within the said media at specific frequency will indicate the total complex characteristic impedance of the media.
A matching network will examine the total resultant complex characteristic impedance of the media, and will produce a buffered real impedance (resistance) value percentagely adjusted to match the transmission-line impedance connected at its input. By applying the basics of transmission line concepts (See xe2x80x9cThe American Radio Relay League Handbook,xe2x80x9d 76th edition, pages 19-3 (1999)), the generated EM-energy is divided within the transmission line into two partsxe2x80x94one part is the xe2x80x9cforwardxe2x80x9d or xe2x80x9cincident power,xe2x80x9d which travels outwardly along the line from the source until it reaches the load (inspected media), where it is then completely absorbed due to the match status. The other part is the xe2x80x9creflected power,xe2x80x9d which is energy reaching the end of the transmission line (matching network input), and is reflected back toward the source that is due to the mismatch status.
The bidirectional coupler is used to instantly sample the two power values within the transmission line, where it detects the forward power before it is transmitted, and the reflected power, which is not released at all from the transmission line (closed system). These two power values are generally free from any ambient electrical interference or noises because the forward wave is sampled before it is transmitted and the reflected wave that has never been transmitted or released from the said transmission-line. That is why amplifying the extracted impedance match variations is safely applicable to great gain levels (few million times). However the system sensitivity and stability mainly depends on the design quality of the device in addition to the mechanical stability of the inspected media.
Various prior art has adapted radar techniques to detect minute body movements by transmitting ultrasound, light, laser, or EM-waves to the target of interest. Through measuring the time-delay or the shift in the phase/frequency (Doppler effect) of the return waves reflected back from the surface of the target, the target movements are detected.
The patent to Geiger, U.S. Pat. No. 6,150,941, discloses a method for noninvasive baby monitoring based on radar techniques, which is achieved by transmitting ultrasonic waves towards the target of interest and picking up the echo return by a microphone. The patent to Corn, U.S. Pat. No. 6,062,216, discloses a similar detection system but utilizes a laser beam. The patents to Allen, U.S. Pat. No. 4,085,740, and to Sharpe, U.S. Pat. No. 4,958,638, both disclose a similar detector, but utilizing EM-waves.
Many other patents suggested the exploiting of parasitic effects of the target on the antenna impedance, such as by utilizing near field or dielectric resonator effects. In this matter the patent to Wolff, U.S. Pat. No. 5,670,886, which is based on the near field effect, is intended for detecting the movements of metallic-type activated targets. This is achieved by electromagnetically charging the metallic surface of the target through directing EM-waves toward the subjected surface, due to what is the so-called virtual capacitance, which occurs between antenna and target surfaces. The feedback of the opposite-polarity charged object would affect the antenna impedance. This is influenced by the reflected waves from the target.
The method of Wolff is intended for detecting metallic-type, nonconcealed objects in close proximity (a few millimeters). This is due to the limitations of the near field effect.
The patent to Boyko, U.S. Pat. No. 3,599,197, discloses a method for detecting moving objects based on coaxial line resonator capacitatively coupling a radiator to comprise an active antenna. The impedance variation of the radiating antenna will influence the center frequency of the previously tuned cavity resonator, which then influences the selectivity of the receiving circuit.
The present invention has many advantages over all the prior arts. It has much higher sensitivity over a wider range of ambient conditions, and additionally concealed metallic and nonmetallic objects are detectable at greater distances. Also, the chosen frequencies utilized by prior art are found in ultra-high ranges, such as high microwave and UHF bands, which are subject to parasitic behavior, which is clearly a disadvantage in circuitry design.
The prior art has no flexibility over the geometry or size of the transmitting antennas.
It is a specific object of the present invention to provide a concealed, moving-object detection system in which the actual total complex characteristic impedance of the inspected media is examined directly (nonreactively) by the output buffering stage (matching network).
It is another object of the present invention to track the target movements by monitoring the resulting forward and reflected waves, which are free from ambient interference and noises. The resulting waves basically occur on the basis of the transmission line impedance match and mismatch concepts. Moreover the monitored waves are sampled before being released from the transmission line.
It is still another object of the present invention to provide an interfacing buffer stage between the monitoring circuits and the real free space. This is achieved by the use of the matching network to match the impedances of the RF transmitter/transmission line with the scrutinized media. In addition, and due to its structure, it acts as a harmonic reject filter, which is based on inductive-capacitative (LC) type circuits, from any of the T-, L-, or Pi-type filter networks.
The present invention can be considered as a closed system due to the absence of any receiving mechanism, which increases the sensitivity to extremely high levels. However, practical observations of the primary prototype device proved that it was possible to detect through a cement wall slight movements of the human finger at a distance longer than a meter.
Considering the present invention as a closed system will make it very difficult to effect intrusion into the area under scrutiny, without initiating the system. This is a basic essential to any compact security systems.
The proposed invention, as an example, can be used to detect the infestation by stem borers, which attack deep inside the tree trunk. This can be achieved through creating a stable EM-field around the tree trunk by a balanced-type, encircling antenna.
Then the complex impedance structure of the tree trunk matches the transmitter output impedance through a matching network. The EM-energy passes through a bidirectional coupler, which produces the VF and VR signals. By the use of DC-blocking capacitors (High Pass Filters-HPF), the variable values which indicates the movement parts of the load from the resultant VF and VR will pass only through these capacitors.
These quite small variable signals are then directed to a linear circuit called an equation processor, which combines both variable signals by utilizing the selected equation, e.g., loss coefficient (VR/VF), or others.
The output signal from the equation processor then can be greatly amplified to a level where it can drive a visual or audio alarm indicator. The same general method described above can similarly be adapted to achieve all the applications aforementioned.